RIS 2015-10, Applicability of ASME Code Case N-770-1 as Conditioned in 10 CFR 50.55a, Codes and Standards, to Branch Connection Butt Welds
| ML15068A131 | |
| Person / Time | |
|---|---|
| Issue date: | 07/16/2015 |
| From: | Kokajko L Division of Policy and Rulemaking |
| To: | |
| Mensah, Tanya 415-3610 | |
| Shared Package | |
| ML15068A069 | List: |
| References | |
| TAC MF3996 RIS-15-010 | |
| Download: ML15068A131 (5) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001 July 16, 2015 NRC REGULATORY ISSUE SUMMARY 2015-10
APPLICABILITY OF ASME CODE CASE N-770-1 AS CONDITIONED IN 10 CFR 50.55a, CODES AND STANDARDS, TO BRANCH CONNECTION BUTT WELDS
ADDRESSEES
All holders of an operating license or construction permit for a pressurized water nuclear power reactor under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.
INTENT
The U.S. Nuclear Regulatory Commission (NRC) is issuing this regulatory issue summary (RIS)
to inform addressees about reactor coolant system (RCS) Alloy 82/182 branch connection dissimilar metal nozzle welds that may be of a butt weld configuration and therefore require inspection under 10 CFR 50.55a(g)(6)(ii)(F), Augmented ISI [inservice inspection]
requirements: Examination requirements for Class 1 piping and nozzle dissimilar-metal butt welds. This RIS also informs addressees of a licensees recent misclassification and missed inspections of RCS Alloy 82/182 dissimilar metal butt welds in branch connections of primary coolant loop piping. This RIS requires no action or written response on the part of an addressee.
BACKGROUND INFORMATION
Inspection of Class 1 piping and nozzle dissimilar metal butt welds that rely on Alloy 82/182 material for structural integrity is mandated in 10 CFR 50.55a(g)(6)(ii)(F). This regulation incorporates ASME Code Case N-770-1, Alternative Examination Requirements and Acceptance Standards for Class 1 PWR [pressurized-water reactor] Piping and Vessel Nozzle Butt Welds Fabricated with UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities. Code Case N-770-1 sets alternative examination requirements and acceptance standards to those included in the ASME Code,Section XI,
Table IWB-2500-1, Examination Category B-F and Examination Category B-J, for Class 1 PWR piping and vessel nozzle butt welds fabricated with Alloy 82/182 weld filler metal. This nickel alloy material is susceptible to primary water stress-corrosion cracking (PWSCC), which, if undetected, can challenge the leak tightness and structural integrity of the reactor coolant pressure boundary.
Code Case N-770-1, as incorporated into NRC regulations by 10 CFR 50.55a(g)(6)(ii)(F),
pertains to butt welds, irrespective of whether the butt weld is circumferential or a branch connection. These regulations require volumetric and surface inspection of all pressure ML15068A131 retaining Class I PWR piping and vessel nozzle butt welds fabricated from Alloy 82/182 materials which are nominal pipe size (NPS) 2 or larger. These regulations also require visual examination of all pressure retaining Class I PWR piping and vessel nozzle butt welds fabricated from Alloy 82/182 materials which are NPS 1 or larger. Subsection NB-3643.2 of Section III of the ASME Code defines acceptable joints for branch connections, including branch components that are attached to the main piping run by welding per NB-4244 or NB-4246.
Full-penetration nozzle branch welds constructed in accordance with NB-4244(a) or NB-4246(a)
are butt welds, as shown in Figures NB-4244(a)-1 and NB-4246(a)-1, respectively. In accordance with 10 CFR 50.55a, the ASME Code, and Owner Requirements, licensees are required to establish the categorization of each branch connection weld.
SUMMARY OF ISSUE
In February 2014, NRC inspectors identified several welds at the Palisades Nuclear Plant that should have been included within the scope of the 10 CFR 50.55a(g)(6)(ii)(F) inspection population, which resulted in a request for relief submitted on February 25, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14056A533). The design of Palisades Nuclear Plant includes nine Alloy 600 branch connection nozzles of NPS 2 and greater that are joined to carbon steel primary coolant loop piping using Alloy 82/182 weld material. Of these nozzles, four are primary coolant loop drain nozzles, two are nozzles for pressurizer spray lines, two are nozzles for charging lines, and one is a combined primary coolant loop drain and letdown nozzle. The joint configuration of these welds was consistent with ASME Code,Section III, Figure NB-4244(a)-1, Nozzles Joined by Full Penetration Butt Welds. However, the licensee failed to classify these welds as butt welds. As a result, the licensee did not complete the volumetric inspections required by 10 CFR 50.55a(g)(6)(ii)(F).
Specifically, 10 CFR 50.55a(g)(6)(ii)(F)(1) states that Licensees of existing, operating pressurized-water reactors as of July 21, 2011, must implement the requirements of ASME
Code Case N-770-1, subject to the conditions specified in paragraphs (g)(6)(ii)(F)(2) through
(10) of this section, by the first refueling outage after August 22, 2011.
The NRC issued a noncited violation to Palisades Nuclear Plant for failure to thoroughly evaluate the scope of welds susceptible to PWSCC and perform the volumetric examinations as required by NRC regulations. Additional details are provided in Palisades Nuclear Plant Integrated Inspection Report 05000255/2014002 (ADAMS Accession No. ML14127A543). On March 12, 2014, the NRC granted verbal authorization for proposed alternative RR-4-18 to the licensee (ADAMS Accession No. ML14073A274) and stated that the licensee could implement the approved alternative to 10 CFR 50.55a(g)(6)(ii)(F). The proposed alternative requires that the licensee perform enhanced leakage monitoring during the current operating cycle and perform the required volumetric examinations during the next refueling outage.
By letter dated September 4, 2014, the NRC staff issued the formal safety evaluation for the licensees proposed alternative RR-4-18 (ADAMS Accession No. ML14223B226). Subsequent to the issuance of the noncited violation to the licensee, the licensee requested from ASME an interpretation of Code Case N-770-1. By letter dated March 10, 2014, (under record number
14-3821) the ASME Standards Committee interpreted Code Case N-770-1 as applying only to circumferential butt welds.
1 https://cstools.asme.org/InterpretationsPDF/BPVC-XI-Interp_Stnd-63_2015_Jan.pdf By letter dated June 23, 2014, (ADAMS Accession No. ML14169A094), the NRC staff responded to ASME concerning its interpretation of Code Case N-770-1. In that letter, the NRC
staff reiterated that the inspection requirements in 10 CFR 50.55a(g)(6)(ii)(F) apply to Class 1 piping and nozzle dissimilar metal butt welds fabricated with Alloy 82/182, including branch connection butt welds.
The NRC expects that licensees will review this information for applicability to their Alloy 600
management plan to ensure all applicable butt welds are being inspected as required by NRC
regulations. In accordance with 10 CFR 50.55a(g)(6)(ii)(F), the NRC requires all butt welds using Alloy 82/182 material that are NPS 2 or greater, including branch connection butt welds, to be volumetrically inspected.
BACKFITTING AND ISSUE FINALITY DISCUSSION
This RIS informs the addressees of the NRC staffs position with respect to the volumetric inspection of RCS Alloy 82/182 dissimilar metal butt welds, and of recent NRC enforcement actions concerning the misclassification and missed inspection of such welds under 10 CFR 50.55a(g)(6)(ii)(F). This RIS does not impose a new or different regulatory staff position interpreting the Commissions regulations pertaining to such welds. The RIS requires no written response or action beyond that already required by NRC regulations. Therefore, this RIS does not represent backfitting as defined in 10 CFR 50.109(a)(1), nor is it otherwise inconsistent with any issue finality provision in 10 CFR Part 52. Consequently, the NRC staff did not perform a backfit analysis.
FEDERAL REGISTER NOTIFICATION
The NRC published a notice of opportunity for public comment on the draft RIS in the Federal Register (79 FR 63446) on October 23, 2014. The public comment period was extended in the Federal Register (79 FR 70897) on November 28, 2014, to allow more time for members of the public to develop and submit their comments. The agency received comments from five commenters. The staff considered all comments, which resulted in minor clarifications to the RIS. The evaluation of these comments and the resulting changes to the RIS are discussed in a publicly-available memorandum, which is in ADAMS under Accession No. ML15068A119.
CONGRESSIONAL REVIEW ACT
This RIS is not a rule as defined in the Congressional Review Act (5 U.S.C. §§ 801-808).
PAPERWORK REDUCTION ACT STATEMENT
This RIS does not contain new or amended information collections requirements that are subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.). Existing requirements were approved by the Office of Management and Budget (OMB), approval number
3150-0011.
PUBLIC PROTECTION NOTIFICATION
The NRC may not conduct or sponsor, and a person is not required to respond to, an information collection unless the requesting document displays a currently valid OMB control number.
CONTACT
Please direct any questions about this matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
/RA/
Lawrence Kokajko, Director Division of Policy and Rulemaking Office of Nuclear Reactor Regulation
Technical Contact:
Jay Collins, NRR Josh Kusnick, RES
301-415-4038 301-251-7963 E-mail: Jay.Collins@nrc.gov E-mail: Joshua.Kusnick@nrc.gov Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library/Document Collections.
ML15152A486 *via e-mail TAC MF3996 OFFICE LA: PGCB/LA RES/DE/CIB NRR/DE/EPNB BC:NRR/DE/EPNB D:NRR/DE
NAME ELee JKusnick* JCollins* DAlley* JLubinski (MJfor)*
DATE 03/12/15 03/12/15 03/18/15 03/26/15 03/30/15 OFFICE D:NRR/DORL D: RES/DE BC: OE/EB NRR/PMDA OIS
NAME MEvans* BThomas* KHanley* LHill* TDonnell*
DATE 04/03/15 04/02/15 04/07/15 04/06/15 04/09/15 OFFICE OGC NLO PM:NRR/PGCB BC: NRR/PGCB LA: PGCB/LA D:NRR/DPR
NAME SClark* TMensah* SStuchell* ELee (ABaxter for) AMohseni DATE 04/27/15 07/08/15 07/08/15 07/09/15 07/09/15 OFFICE D:NRR/DPR
NAME LKokajko DATE 07/16/15